Mobile Internet Protocol (IP) is a protocol that allows mobile devices such as mobile computers and mobile stations to roam between various networks and sub-networks at various location while maintaining internet or wide area network connectivity. Without Mobile IP or related protocols, a mobile device would not be able to stay connected while roaming between these different networks. This is because the IP address required for any node or device to communicate over the Internet and similar networks is location specific. Each IP address is associated with the particular network or sub-network on which the device resides. This makes it difficult for a device to continue to use the Internet or other networks when the device is mobile. To address this problem, the Mobile IP protocol has been developed and implemented. An implementation of Mobile IP is described in RFC 2002 (and further enhanced in RFC 3344) of the Network Working Group in IETF (Internet Engineering Task Force).
Mobile IP therefore provides a mobility function for the mobile devices. In particular, Mobile IP works with mobility in the layer 3 of communication network protocols. Mobile IP layer 3 mobility can be controlled by either the communication network infrastructure components such as an access node, base station, Proxy Mobile IP client or the like or by the mobile device such as an access terminal. When the network controls the Mobile IP, the capability is referred to as Proxy Mobile IP (PMIP). When the mobile device controls the Mobile IP, the capability is referred to as Client Mobile IP (CMIP). There currently is no protocol within Mobile IP that prioritizes the control of the Mobile IP between the PMIP and CMIP-enabled devices. Thus, there can be conflict between PMIP and CMIP when a CMIP-enabled mobile device operates in a PMIP-enabled network.
Thus, there is a need for a mechanism for prioritizing between CMIP and PMIP when both the network and the mobile device provide at least layer 3 Mobile IP. In addition, there is a need for a mechanism that avoids race conditions between CMIP and PMIP when the mobile device and the network do not have a clear understanding of which of the two is to control Mobile IP functionality. These problems apply as well to client-controlled and network-controlled mobility using protocols different from Mobile IP.
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